A developing cartridge includes a developing roller, and is attachable to and detachable from an image forming apparatus.
A developing cartridge according to the prior art includes a gear, and a protrusion. The gear is rotatable from a first position to a second position. The protrusion is provided at the gear, and is movable together with the rotation of the gear to be brought into contact with a lever of an image forming apparatus. The lever is moved by the contact with the protrusion. The image forming apparatus determines a specification of the developing cartridge as a result of detection of the movement of the lever. The gear includes a teeth lacking portion. Meshing engagement between the gear and a drive gear is released when the teeth lacking portion faces the drive gear. Thus, rotation of the gear is stopped to stop movement of the protrusion.